This invention relates to an apparatus for transmitting light signal to and from a movable trolley or the like via a fiber optic cable at any point along the cable.
Fiber optic transmission cables have the advantages of low transmission loss, wide bandwidth, light weight, insensitivity to induced electromagnetic signals, and small size over electrical wires or cables, but they cannot receive and/or transmit light signals at any point except their ends or junctions. With current usage of optical cables it is necessary that they be branched off to enable the control of an optical, heat, electrical, or power source, or a robot device.
FIG. 1 shows a prior art arrangement in which an optical cable is used to supply signals to a movable object, such as a robot. A flexible optical cable 2 is connected to a movable object 1, and a stationary optical cable 4 is connected to the flexible cable 2 at a fixed point 3. The cable 2 may be moved with respect to the fixed point 3. During operation, the flexible cable 2 is trailed on the floor, and is pulled out or extended as required to accomodate movements of the object 1; light signals from the stationary cable 4 are continuously supplied to the movable object 1 through the cable 2. As the movable cable 2 is repeatedly trailed on the floor it is exposed to mechanical damage, however, which greatly decreases its usable life. Further, when the object 1 moves a significant distance a large amount of the cable 2 is needed, which presents problems in its winding and unreeling.